LIBRA´TOR
LIBRA´TOR is in general a person who examines things by a libra; but the name was, in particular, applied to two kinds of persons.1. Librator aquae, a person whose knowledge was indispensable in the construction of aqueducts, sewers, and other structures for the purpose of conveying a fluid from one place to another. He examined by a hydrostatic balance (libra aquaria) the relative heights of the places from and to which the water was to be conducted. Some persons at Rome made this occupation their business, and were engaged under the curatores aquarum, though architects were also expected to be able to act as libratores. (Plin. Ep. 10.50; Frontin. de Aquaed. 105; compare Vitr. 8.6; Cod. 10, 66, 1.) [L.S]
2. Libratores (or libritores, according to some MSS.) were soldiers who are coupled with slingers (funditores) in Tacitus, Tac. Ann. 2.20, 13.39. There is much difference of opinion about them. Some recent writers take them to be engineers of some description engaged in the management of tormenta, and the derivation librare, “to level,” is suggested as though they levelled and directed them. It can be inferred from Marquardt's note (Staatsverwaltung, 2.526) that he also classes them with the managers of tormenta, but he gives no definite statement of his opinion. In Tac. Ann. 13.39, in a fresh sentence after the words “multos tormentis faces et hastas incutere jubet,” we find “libratoribus et funditoribus attributus locus unde eminus glandes torquerent,” from which the inference surely would be that they have nothing to do with the tormenta, and are an arm of the service more like the slingers: and the other passage of Tacitus tells the same way, “funditores libratoresque excutere tela et proturbare hostes jubet: missae et tormentis hastae.” Forcellini conceives slings which discharged stones of a pound weight to explain the libralia or librilia saxa (cp. Caes. Gal. 7.81). If this were a correct view, the key to the precise explanation might be found in Liv. 38.29, where, at the siege of Same in B.C. 189, slingers are described as brought from Achaia, who “a pueris” practised slinging saxa globosa: the force is greater than that of the Balearic slinger, and the sling is not a single thong but a triple “scutale” made stiffly, so that the missile “librata quum sederit velut nervo missa excutiatur:” apparently they could fire more nearly point-blank and with heavier charge. But against this we have first the fact that the libratores were to be distinguished from slingers generally, and not merely from Balearic slingers; and, secondly, the passage of Vegetius, 2.23, which tells us that libralia saxa were thrown by the hand and with less preparation as requiring no sling: and Festus explains librilia as “saxa ad brachii crassitudinem loris revincta.” This suggests the conclusion that the stones were swung by the thong, to which they were fastened, and discharged thong and all. And it is perhaps best to regard the libratores as stone-throwers employed, not with the tormenta, but along with the funditores (cp. the λιθοβόλοι coupled with σθενδονῆται, Thuc. 6.69), throwing with the hand by the thong attached missiles heavier than the glans of the slinger: and the word should probably be connected with the sense of swinging in libro (as in Livy, l.c.), rather than with libra, “a pound.”
[G.E.M]